Remove arc_read_nolock() and align with upstream use of arc_read(). Fixed
NAMED_STREAMS which makes ZFS work with Finder better. Add available memory
lookup to ARC, add hostname lookup to startup. Fix leak of SA nodes in znode.
Do not hold LOCKs when calling vnode_create(). Attempt book keeping in
dnode to track ARC allocations.
Remove conditional lock in zget, left from previous attempts.